Process of treating iron ores.



E. F. GOLTRA.

PROCESS OF TREATING IRON ORES. APPLICATION FILED APR.26, 1910.-

attomwuo r sayings PATENT ora ion.

EDWARD 1r. GOLTRA, or sr. LOUIS, MISSOURI.

PROCESS OF TREATING IRON ORES.

Specification of Letters Patent.

Patented Feb... 13, 1917.

Application filed April 26, 1910. Serial No. 557,709.

and this gangue must be separated from the ore before it can be smelted successfully in the blast furnace. Heretofore this gangue has been washed out with water in the usual hydraulic practice, but since some ores are associated withfrom five to seven times as much gangue as ore, an enormous amount-of water is required for Washing out the gangue. Moreover, this clay gangue is often so pasty that separation by washing is practically an impossibility. As this ore is often in the form of a sintered mass, caused during its geological formation, and, therefore, inherently full of holes, crevices and cavities which have become filled and clogged with clay,'it is impossible to remove the pasty clay gangue from the cavities-by the use of water. The result, therefore, is,

that with the best hydraulic methods and apparatus-heretofore employed, a large art of the clay gangue remains in the ore. 0W this presence of the clay not only hinders the smelting, but also requires a large amount of fuel and flux to overcome and neutralize its presence. This is especially true since the ore, filled as it is with clay, is so dense and 'unporous that the reducing gases cannot penetrate it, and therefore can reach or act only on and with th outer surfaces. It is, of course, a well known fact in physical chemistry that the rapidity of the re-action between. a gas and a solid is proportional to the surfaces of the solid in contact with the gas. An unporous mass, therefore, re-acts very slowly with the gas.

Even where smeltable ore is produced by, washing-away the gangue from the surfaces, the resulting concentrate is so wet that unless it is first dried it cannot be used in the furnace. It will, therefore, be seen that the very hydraulic operation introduces unnecessary fuel losses.

Moreover, brown hematite contains volatile matter mostly in the form of combined moisture or water and this must of course be volatilized during the smelting operation in the blast furnace. Now when we consider that the heat required to drive offmoisture, whether in free or combined form, is extremely large on account of the large value of the latent heat, and when we further consider that this water must be driven ofl in the smeltingfurnace by an expensive fuel, such as coke, the fact will be appreciated that the cost of doing this will necessarily constitute a large proportion of the .total fuel cost of smelting. Moreover, the

presence of this water and clay interferes seriously with the operation of the furnace;

Some of the objects of this invention, therefore, are to devise a process of treating ores, in which the gangue as well as the moisture and volatile matter are by a preliminary treatment separated from the ore, extraneously of the blast furnace, and in which the ore when in the furnace is ,in an ideal condition for the reducing and smelting operations, whereby the operations in the furnace are reduced to those of reduction and melting.

Further objects will appear from the detail description, taken in connection with the accompanying drawing, in which the figure is an elevation, partly in section, of

an apparatus suitable for carrying out the process embodying this invention.

It is to be understood, however, that this apparatus is simply an illustration 'of a suitable one for performing the process, and that various other equivalent and suitable means may be utilized. I

In accordance with this invention the ore and its gangue are heated at a temperature and for a period suflicient to drive ofi the moisture, and to render the gangue easily separable from the ore. The ore and gangue are tumbled to loosen the gangue from the ore, and the ore and gangue are subjected to a strong blast, which by an air washing 0 erationremoves the gangue from the ore.

1e heating is carried on to an extent sufficient not only to drive off the free moisture, but also the conibined moisture or any other volatile matter contained in the. ore. Ihe result, therefore, is that by this preliminary treatment the ore is not only freed of its gangue by an air washing operation, but

is also freed of its moisture and volatile after loosen the gangue from the ore.

been removed not only from around, but also in the ore, and the removal of the gangue and the moisture causes the ore to be in a dried and porous condition. This dried, porous ore is subjected in a blast furnace to heat and reducing gases so as to reduce the' ore to the metallic state.

The ore as mined must be dried slowly and gradually, especially if it contains much clay as a gangue, since a rapid heatlng would cause this clay to become hard and burned to a brick, and it would be thus impossible or exceedingly difficult to thgareor this purpose the wet ore and gangue are subjected to a gradually increasing temperature, beginning at a comparatively low limit and increasing gradually to a comparatively high limit.

Referring now to the accompanying -drawing,.10 designates a long drum 'provided with a number of rings 11 resting on a number of sets of anti-friction rolls 12, in turn supported on a foundatlon, these rolls being placed so as to support. the drum for rotation on a slight incline. The ends .of the drum extend into stationary heads 13 and 14 suitably supported, and the upper head 14 is provided with a hopper 15 adapted to discharge the ore and gangue into the drum. A suction fan 16 is connectedto the upper head 14 and is driven by a suitable motor, so as to create a strong blast in and through the drum 10. A heating device or burner 17 extends through the head 14 so as to heat the blast. This burner may be an ordinary oil burner, but it will be understood that the heating means may be of any suitable construction. The lower head 13 is further provided with an air inlet 21 so as to allow the blast to enter near the burner and be heated thereby, and this head is also provided with a discharge or outlet 18 for the ore. The drum is rotated by a driv- 1ng pinion 19 engaging a gear 20 on the drum and driven from any suitable source of power. The drum is lined with a suitable refractory lining 22, and this lining may also be provided for the heads 13 and 14. The blast furnace A of usual construction, and comprising the usual shaft 23, waist 21 and crucible 25, and provided with the usual twyers 26, performs the smelting treatment of this process. This furnace is provided with a hoist or way B, on which travels a carriage 28 to convey the ore to the top of and discharge it into the furnace. As both furnace and hoist are well known in the art a detail description will be unnecessary.

Where it is desired to discharge the ore directly from the drum 10 into the furnace A, then the bottom end of the hoist may enter a pit below the outlet 18, so that the carriage or conveyer 28 may receive the ore directly from the drum 10. In such a case this outlet is preferably provided with a cut-out slide 27. It is to be understood, of course, that the specific apparatus described and shown is used merely as an illustration of one form of apparatus for carrying out the process embodying this invention, as it will be obvious to any one skilled in the art that the process is susceptible of being performed 'by various and suitable apparatus constructed and arranged otherwise than as in the specific form described and shown.

I The exhaust fan 16 being set into operation, the drum rotated, and the burner or heating device furnishing the heat to the lower end of the drum, a hot blast will pass from the lower to the upper end of the drum. It will, of course, be understood that the temperature in the drum is the greatest at or near its lower end, and that this tem perature wilLdecrease gradually from a maximum at the lower end of the drum to a minimum at the upper end, and conversely the temperature will increase gradually from the upper to the lower end of the drum. The exhaust fan is driven at aspeed suificient to cause the passage through the drum of a strong blast, as distinguished from an ordinary weak air current, that is the blast is of suflicient strength to carry with it particles of material in the drum.

The ore as mined is preferably crushed to a workable size, and is dumped into the hopper 15 and from there discharged into the drum 10. As the drum is rotated it will on account of its inclination and rotation, cause the ore to be gradually carried from the upper to the lower end thereof, the speed of this carrying movement depending, of course, upon the diameter of the drum, its speed of rotation and the inclination given to the drum. As the ore passes along the drum, it is met by the hot blast drawn through the drum, and on account of the gradual temperature gradient from the upper to the lower end of the drum, the wet ore is gradually dried. In its passagedown the drum the ore is tumbled and thrown around so as to shake loose the dry gangue from the ore, this gangue on account of the drying action being rendered brittle and easily separable from the ore, and being separated by the tumbling action of the ore lumps. This combined drying and tumbling action not only shakes loose the surface gangue, but also exposes the gangue in the pores, crevices and cavities in the ore lumps,

and the tumbling action shakes loose and separates the gangue from these cavities. The gangue, which is shaken loose, is pulverized by the tumbling action of the lumps to a fine condition. During therotation of the drum this fine gangue is caugh. by

. drive off the combined moisture, or any other volatile mattergwhich may be contained in the ore. In the tumbling operation the ore. lnmps-will-be cracked so as to enhance the driving off of the moisture, and also enhance the separation of the gangue,

- and this cracking and heating will further separate any silicious gangue which may be in or on the ore. It will thus be seen that the air blast washes the ore and its gangue as in the water washing process, but the blast can enter the crevices in the ore where the water cannot enter, thus thoroughly cleaning the ore of its gangue and leaving it in an open and porous condition. The ore will be further rendered porous by the expulsion of the volatile matter from the interior of the lumps.

The cleared ore as it leaves the drum is in an ideal condition to be used in the subsequent reducing and smelting operations. The moisture, both free and combined, and other volatile matter, have been driven off and the ore has been placed in a dry and porous condition, which is so desirable for' the reducing and smelting operation. When,

i -therefore, this ore is discharged into the blast furnace, it is in an ideal condition to be acted upon by the reducing gases and the heat, to reduce it to the metallic state. The porous condition of the ore ,permits the gases to fully penetrate the. same, so as to cause a large surface contact between the reducing gases and the ore. .A minimum amount of reducing gases and of a minimum density are therefore sufficient for the reducing operation. Since the ore is cleaned and devoid of moisture, the amount of flux and fuel can be a mimimum, as no more flux is necessary than required for the fluxing of any slight amount of silica remaining with the iron, and no more fuel is necessary than required for the smelting of the iron content. The fuel consumption is therefore materially reduced, as a cheap fuel can be used in the cleaning treatment.

The length of the drum, its diameter, its incline, the speed of rotation and the temperatures will vary with different ores and with their condition as to dampness, the amount of clay in them and the amount of combined moisture and volatile matter. As a practical case, where brown hematite conoughly dried, and still dry gradually enough I so that it will not become hard baked. The blast can, however, be regulated to suit conditions, the object being to cause this draft to carry the pulverized gangue ofl, and therefore deliver for smelting an ore which is cleaned substantially of all of its 'gangue.

It will be noted that as the ore leaves the drum it is not only cleaned, but is at a high temperature, namely at or near the temperature at the lower end of the drum.

Where, therefore, the blast furnace is used directlyin conjunction with the drum and where the ore is discharged directly from the drum into the furnace without allowing the ore to cool, the heat in the ore can be conserved and utilized, so that it is not necessary in such a case to first raise this ore to that temperature in the blast furnace. In addition, therefore, to the elimination of the heat. required to drive off the moisture and other volatile matter, the heat ap-. plied in the air washing operation is also conserved.

- It is obvious that various changesmay be made in the details of the process and in the apparatus without departing from the spirit of this invention and it is therefore to be understood that this invention is not to be limited to the specific "details and arrangements ofsteps and apparatus described and shown.

The process of clearing the ore, per s e, is not claimed in this application as it is claimed in my co-pending applications which have now matured into Patents Nos. 957157 and 961121 granted May a, 1910, and June 14, 1910, respectively.

Having thus described the invention what is claimed'isi 1. The process of treating iron ores, comprising heating the ore' and its gangue at aatemperature and for a period sufficient to drive ofi the moisture, and to render the gangue easily separable from the ore, tumbling the ore and its ga'ngue to loosen the gangue from the ore, subjecting the ore and its gangue to a strong blast which removes the gang'ue from the ore, and subjecting the concentrated ore, so prepared, to heat and reducing gases, to reduce the ore to the metallic state.

2. The process of treating iron ores containing gangue, moisture and volatile matter, comprising calcining the ore and its gangue at a temperature and for a period suflicient to drive 01f the moisture and-volatile matter, and to'render the gangue easily separable from the ore, tumbling the ore and its gangue to loosen the gangue from the ore, subjecting the ore and its gangue to a strong blast which removes the gangue from the ore, and subjecting the concentrated'ore, so prepared, to heat and reducing gases, to reduce the ore to the metallic state.

3. The processof treating iron or es con= taining moist clay, etc., as a gangue, com prising heating the ore and its gangue at a temperature and for a period sufiicient to drive ofi the moisture, and to render the gangue easily separable from the ore, tumbling the ore and its gangue to shake-loose the gangue from the ore, and to pulverize the gangue by said tumbling action, subjecting the ore and gangue to a strong blast which sweeps, cleans and removes the gangue from the ore, and subjecting the concentrated ore, so prepared, to heat and reducing gases, to reduce the-ore to the metallic state.

4. The process of treating iron ores containing clay, etc., as a gangue and containing moisture and volatile matter, comprising calcining the ore and its gangue at a temperature and for a period suflicient to drive off the moisture and volatile matter, and to render the gangue easily separable from the ore, tumbling the. ore and its gangue to shake loose the gangue from the ore, and to pulverize the gangue by said tumbling actiOIl, subjecting the ore and gangue to a strong blast which sweeps, cleans and removes the gangue from the ore, and subjecting the concentrated ore, sopre-v pared; to heat and reducing gases, to-reduce the ore to the metallic state.

In testimony whereof I aflix my signature in presence of two witnesses.

' EDWARD F. GOLTRA.

Witnesses J. H. BRUNINGA,

ARTHUR L. BRYANT. 

